1. Field of the Invention
The present invention is directed to expansion-deflection couplings and more particularly to couplings for sealingly connecting the opposed spaced apart ends of two conduits which might be subject to linear or angular misalignment or which might be susceptible of expansion or contraction.
2. Prior Art
In numerous construction projects it is often necessary for conduits to be embedded in large concrete pours or blocks which may be subject to movement relative to each other. Such relative movement necessitates the use of expansion-deflection type couplings in conduits running between adjacent concrete pours to prevent damage to the conduit or the cables inside. Expansion-deflection type couplings are also necessary to span expansion joints in bridges wherein the structural movement would be caused by thermal expansion-contraction or by heavy vehicular traffic. Long underground conduit runs are commonly used to interconnect widely spread facilities and the use of expansion-deflection couplings will accommodate conduit movement in such long runs caused by ground settling or seismic forces. Likewise such couplings are necessary to provide the necessary flexibility at the service entrance to a building to accommodate movement caused by high winds or earthquakes or to provide the necessary flexibility to compensate for structural movement caused by settling.
Expansion-deflection type couplings can be installed indoors, outdoors, buried underground or embedded in concrete in non-hazardous areas. They can be used with standard rigid conduit and PVC rigid conduit. Use with PVC requires rigid metal conduit to PVC conduit adapters. Expansion-deflection couplings provide a flexible and watertight connection between sections of conduit which are vulnerable to stresses and displacement as a result of the above mentioned causes.
Prior art type expansion-deflection couplings utilize only a neoprene sleeve which is clamped to the external surface of hub end fittings which are adapted to be threaded on the ends of opposing conduits. In such prior art constructions the sleeve does not completely enclose the grounding strap or cover the strap to hub attachment points. Furthermore, such prior art couplings do not provide an internal sleeve which will span the gap between the hubs to separate the grounding strap from the wiring or maintain a uniform internal diameter for the passage of wires regardless of the expansion or deflection of the flexible sleeve. Finally, the prior art devices secure the grounding straps to the hubs in the vicinity of the wrenching surface of the hubs thereby exposing said connections to possible damage during wrenching with attendant interruption of the ground connection.